A data transmission standard such as Bellcore Synchronous Optical Network (SONET) involves transmission of basic serial information in a serial bit stream with a basic bit rate of 51.840 Mbits/s. The data is typically converted from serial to parallel data format, wherein the parallel data clock rate is a fraction of the serial data clock rate, and is converted from parallel to serial data format, at various parts of the system carrying and translating the data.
It is desirable to use integrated circuits to provide the conversion. The result of a serial-to-parallel conversion allows other logic circuits on the integrated circuit to process the data at the slower parallel clock rate. The need for the parallel-to-serial conversion is that the result of that data processing usually is transmitted using the same serial format. Both circuits operate mainly on the serial clock rate thus requiring custom design since standard logic libraries are usually not capable of the serial clock speeds.
While the function of a particular design may not change over its lifetime, integrated circuit technology used to fabricate the designed structure can change over the lifetime of the design. As new integrated circuit technology becomes available, the custom logic must be maintained, which is a very expensive engineering activity.